Truing device

ABSTRACT

A truing device for truing a grinding tool having a specified grinding profile, includes at least one first truing region and a second truing region connected thereto. The first truing region has a first specification for sharpening the grinding profile of the grinding tool and the second truing region has a second specification, different from the first specification, for restoring the grinding profile of the grinding tool. The first truing region has a greater volume than the second truing region, the truing device has a longitudinal axis, the two truing regions are arranged one behind the other in the direction of the longitudinal axis, and the truing device is substantially cuboid.

BACKGROUND OF THE INVENTION

The invention concerns a dressing apparatus for dressing a grinding toolprovided with a predetermined grinding profile and a method of dressinga grinding tool by means of at least one such dressing apparatus.

Grinding tools have to be dressed after a given period of time ingrinding operation, in which respect a number of processes aredistinguished from each other in terms of the dressing operation.

One of those processes involves sharpening the grinding profile of thegrinding tool. In that procedure for example impurities are removed,abrasive grains which have become blunt are removed, fresh abrasivegrains are exposed and/or abrasive grains are sharpened, for example bybreaking them.

A further process involves restoring the grinding profile of thegrinding tool. In the course of that process binder material, grindingdeposits and/or abrasive grains are removed, with the aim of restoringthe predetermined grinding profile of the grinding tool.

Dressing tools with a unitary specification which is based on acompromise between the different dressing processes are known from thestate of the art.

That has a detrimental on the maximum operating lifetime of the grindingtool, that is to say the period of time between the first-off use of thegrinding tool and the time at which the grinding profile of the grindingtool is damaged to such an extent that the grinding tool has to bereturned to the manufacturer in order to mechanically reconstruct theoriginal grinding profile, preferably by electrical discharge machining.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a dressing apparatuswhich is improved over the state of the art and which permits inparticular an increased operating lifetime of the grinding tool dressedby the dressing apparatus. A further object is that of providing amethod of dressing a grinding tool by means of at least one suchdressing apparatus which permits in particular efficient dressing of agrinding tool and an increased operating lifetime of the grinding tool.

In the dressing apparatus according to the invention it is thereforeprovided that the dressing apparatus includes at least a first dressingregion and a second dressing region connected thereto, wherein the firstdressing region has a first specification for sharpening the grindingprofile of the grinding tool and the second dressing region has a secondspecification differing from the first specification for restoring thegrinding profile of the grinding tool, the first dressing region is of alarger volume than the second dressing region, the dressing apparatushas a longitudinal axis, the two dressing region are arranged insuccession in the direction of the longitudinal axis and the dressingapparatus is of a substantially cuboidal configuration.

The dressing apparatus therefore includes at least two dressing regions,wherein one of the two dressing regions of optimized for the process ofrestoring the grinding profile and the other of the two dressing regionsis optimised for the process of sharpening. Depending on which specificprocess is implemented the corresponding dressing region is specificallyused. It has been found in tests that the service life of the grindingtool dressed with such a dressing apparatus can be almost doubled incomparison with a dressing apparatus in which a compromise is made inthe design thereof as between the restoration process and the sharpeningprocess.

An advantage in that respect is also the fact that the two dressingregions are connected together. Alternatively it would also be possibleto consider using two different dressing apparatuses each having arespective dressing region, wherein one of the two dressing apparatusesis designed for the process of restoring the grinding profile and theother of the two dressing apparatuses is designed for the sharpeningprocess. It will be noted however that the two dressing apparatuseswould then have to be used alternately, which involves an increasedlevel of complication and involvement in positioning. In comparisontherewith, it is possible with the present dressing apparatus for it tobe positioned only once, for example in a feed device, and for firstlythe second and then the first dressing region to be used up at least forthe predominant part thereof. In that way there is automatically achange between the process of restoring the grinding profile and thesharpening process, without the position of the dressing apparatusrelative to the feed device having to be changed.

In that respect it has proven to be particularly desirable in relationto handling of the dressing apparatus for the dressing apparatus to havea longitudinal axis and for the two dressing regions to be arranged insuccession in the direction of the longitudinal axis.

Furthermore, in relation to handling the dressing apparatus it hasproven to be advantageous that the dressing apparatus is of asubstantially cuboidal configuration, preferably of a length of 150 mmto 250 mm, particularly preferably 180 mm to 200 mm, and/or a width of25 mm to 75 mm, particularly preferably about 50 mm, and/or a thicknessof 2.0 mm to 10.0 mm, particularly preferably about 3.0 mm, 4.0 mm or5.5 mm.

And finally, in relation to handling the dressing apparatus, it is alsoadvantageous that the dressing apparatus has a holding region forholding the dressing apparatus when dressing the grinding tool, whereinpreferably the holding region is of an abrasive grain-less nature and/oris secured by adhesive or sintering, and/or substantially comprises awater-soluble material. Without that holding region the dressingapparatus would have to be held at one of the two dressing regionswhich, in the region used for holding purposes, could no longer be usedfor dressing and would have to be disposed of as waste.

In principle the holding region can already be manufactured inmanufacture of the two dressing regions. Then a material is used, whichwithstands pressure and temperature in manufacture of the dressingregions. Here for example an inexpensive ceramic material presentsitself as an option, similarly to a “low-cost core” in the case ofceramic grinding discs.

Alternatively it is possible to fit the holding region only aftermanufacture of the two dressing regions, for example using adhesive. Inthat case it is possible to use the most widely varying materials likefor example wood, plastic or organic materials. A prerequisite issufficient strength and the possibility of securing it to the dressingregions by adhesive.

In the situation where the material of the holding region iswater-soluble it would be possible to easily dispose of or recycle theholding region after use thereof, by dissolving in water.

Because the first dressing region is of a larger volume than the seconddressing region it is possible to set an optimum relationship betweenthe dressing step of profiling and the dressing step of sharpening. Morespecifically in practice the situation is frequently such that agrinding tool is profiled at a lesser degree of frequency than it issharpened, and that a smaller volume of dressing material is consumed inthe profiling operation in comparison with the shaping operation.

In that respect it has been found to be advantageous for the volume ofthe first dressing region to be about 4 to 7 times, preferably about 6times, greater than the volume of the second dressing region.

The specification of the first and second dressing regions depends onthe specific configuration of the grinding tool and the specific use ofthe grinding tool. In general the specification of the second grindingregion will be selected to be more aggressive than the specification ofthe first dressing region, whereby the specification of the seconddressing region is adapted to remove more abrasive grain and/or bindermaterial, in comparison with the specification of the first dressingregion.

For example, for dressing grinding tools which are used for grindingworkpieces in the form of glass panes it is appropriate for the firstspecification to be of a mean pore size of 200 to 500 μm, preferablyabout 350 μm, and/or to have white corundum as the abrasive, and/or tohave an abrasive grain with a grain size of 120 to 220 mesh, preferablyabout 180 mesh.

In regard to the second specification it is advantageous for the secondspecification to be of a porosity in the range of 10 to 15 percent byvolume and/or to have a mixture of white corundum and pink corundumand/or red corundum as the abrasive grain, and/or to have an abrasivegrain of a grain size of 35 to 100 mesh, preferably about 55 mesh.

White corundum comprises up to over 99.9% Al₂O₃ (aluminium oxide) andhas a high level of hardness and heat resistance up to 2000° C. Pinkcorundum has low proportions of foreign substances which impart asomewhat higher grain toughness thereto and permit the use thereof forshaping and profile grinding by virtue of a higher degree of edgestrength. Otherwise it corresponds to white corundum. The foreignsubstances added are for example chromium or titanium as oxide in themelting process. For the situation where chromium oxide is added as theforeign substance it is possible to distinguish pink corundum and redcorundum from each other by virtue of the fact that pink corundumcontains approximately 0.25% Cr₂O₃ while red corundum contains about 2%Cr₂O₃.

A ceramic binder is suitable as the binding agent both in the case ofthe first and also in the case of the second specification.

As stated in the opening part of this specification protection is alsoclaimed for a method of dressing a grinding tool by means of at leastone dressing apparatus according to the invention, wherein the methodincludes a first method step in which the grinding profile of thegrinding tool is restored by means of the second dressing region of theat least one dressing apparatus and a second method step in which thegrinding profile of the grinding tool is sharpened by means of the firstdressing region of the at least one dressing apparatus.

Preferably the first method step takes place before the second methodstep. The two method steps however could also be carried out in thereverse sequence in time.

In addition it is desirable for the first method step to be repeated ata first frequency N1 before the second method step is carried out andfor the second method step to be repeated at a second frequency N2 afterconclusion of the first method step which is repeated at the frequencyN1, wherein N1<N2.

It has also proven to be advantageous that, before the second methodstep, the first method step is carried out or repeated until at least apredominant part of the second dressing region is consumed and afterconclusion of the first method step the second method step is carriedout or repeated until at least a predominant part of the first dressingregion is consumed. In that way an automatic change can be implementedbetween the profiling dressing step and the sharpening dressing step.

Further advantageous embodiments of the method provide that:

-   -   before the first method step and/or between the first and second        method steps and/or after the second method step and/or between        the possibly provided repetition of the first or second method        step the grinding tool is used a plurality of times for grinding        at least one workpiece, preferably a glass pane, and/or    -   the dressing apparatus has a holding region for holding the        dressing apparatus when dressing the grinding tool and the at        least one dressing apparatus is held at least during the first        and second method steps at least at the holding region in a feed        device, and/or    -   the method is carried out sequentially with a plurality of        successive dressing apparatuses, wherein a further dressing        apparatus is fed, preferably from a magazine, as soon as a        preceding dressing apparatus is consumed at least for the        predominant part, and/or    -   the method takes place in automated fashion at least for its        predominant part.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention are described more fullyhereinafter by means of the specific description with reference to thedrawings in which:

FIG. 1a is a diagrammatic perspective view of an arrangement comprisinga workpiece, a grinding tool and a dressing apparatus,

FIG. 1b is a diagrammatic side view of a grinding operation on aworkpiece, wherein the illustrated dressing apparatus is out ofengagement,

FIG. 1c is a diagrammatic side view of an arrangement comprising aworkpiece and a grinding tool before the beginning of a grindingoperation,

FIG. 1d is a diagrammatic side view of an arrangement comprising aworkpiece and a grinding tool during a grinding operation,

FIG. 2a is a diagrammatic perspective view of a first preferredembodiment of a dressing apparatus,

FIG. 2b is a diagrammatic perspective view of a second preferredembodiment of a dressing apparatus,

FIG. 3 is a diagrammatic perspective view of an arrangement comprising agrinding tool and two dressing apparatuses in a first embodiment,

FIG. 4a is a diagrammatic side view of an arrangement comprising agrinding tool and a plurality of dressing apparatuses in a secondembodiment,

FIG. 4b is a diagrammatic side view of an arrangement comprising agrinding tool and a plurality of dressing apparatuses in a thirdembodiment,

FIG. 4c is a diagrammatic side view of an arrangement comprising agrinding tool and a plurality of dressing apparatuses in a fourthembodiment,

FIG. 5 is a diagrammatic enlarged view of a part of a dressingapparatus,

FIG. 6a is a diagrammatic side view of the dressing step of profiling agrinding tool by means of a dressing apparatus,

FIG. 6b is a diagrammatic side view of the dressing step of sharpening agrinding tool by means of a dressing apparatus, and

FIG. 7 is a diagrammatic view illustrating a method of dressing agrinding tool which is used for processing a workpiece, by means of atleast one dressing apparatus.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a shows a grinding tool 2 mounted rotatably about an axis ofrotation 33. The grinding tool 2 has a groove-shaped grinding profile14, with which the edge 51 of a workpiece 15 in the form of a glass panecan be ground. It will be appreciated that the invention is not limitedto dressing a grinding profile of a groove-shaped configuration of agrinding tool.

The workpiece 15 is mounted displaceably and rotatable in all directions52 in space. In addition there is provided a feed device 16 in which adressing apparatus 1 is mounted. The dressing apparatus 1 is held in thefeed device 16 in positively locking relationship. In addition there isprovided a hold-down clamp 30 for holding the dressing apparatus 1.

As FIG. 1b shows the workpiece 15 can be arranged for example by way ofholding devices 31 on a carrier 32, wherein the holding devices 31and/or the carrier 32 can be displaceable in the directions 52 in space.

As FIG. 1b further shows the grinding tool 2 can be clamped in aclamping device 28 of a grinding machine 26.

The sequence of FIGS. 1c and 1d diagrammatically shows the operation ofgrinding the edge 51 of the workpiece 15 by means of the grinding tool2. In the position shown in FIG. 1c the edge 51 of the workpiece 15 isspaced from the grinding profile 14 of the grinding tool 2. In theposition shown in FIG. 1d the grinding profile 14 of the grinding tool 2is in engagement with the edge 51 of the workpiece 15. In that casematerial of the workpiece 15 is removed by a relative movement of thegrinding profile 14 and the abrasive grains 13 therein relative to theworkpiece 15.

In accordance with a first preferred embodiment shown in FIG. 2a thedressing apparatus 1 has a first dressing region 3 and a second dressingregion 4 connected thereto, wherein the first dressing region 3 has afirst specification for sharpening the grinding profile 14 of thegrinding tool 2 and the second dressing region 4 has a secondspecification, differing from the first specification, for restoring thegrinding profile 14 of the grinding tool 2, and wherein the firstdressing region 3 is of a larger volume than the second dressing region4.

The dressing apparatus 1 is of a substantially cuboidal configuration,wherein the length of the dressing apparatus 1 is denoted by reference6, the width is denoted by reference 7 and the thickness by reference 8.

The dressing apparatus 1 has a longitudinal axis 5. The two dressingregions 3 and 4 are arranged in succession in the direction of thelongitudinal axis 5.

In accordance with a second preferred embodiment shown in FIG. 2b thedressing apparatus 1, in comparison with the first preferred embodiment,has an additional holding region 9 for holding the dressing apparatus 1when dressing the grinding tool 2 wherein the holding region 9 is of anabrasive grain-less nature.

Naturally the dressing apparatus 1 in accordance with the firstpreferred embodiment can also be held in the dressing operation, morespecifically for example at the dressing region 3, as can be seen interalia from FIG. 3.

In the embodiment shown in FIG. 3 the feed device 16 has a magazine 17for two dressing apparatuses 1 which are arranged in the magazine 17 insuccession in the direction of the longitudinal axis of the dressingapparatuses 1. One of the dressing apparatuses 1 projects by a distancefrom the feed device 16. That dressing apparatus 1 is now used firstlyfor dressing the grinding tool 2, more specifically until the dressingapparatus 1 is used up to such an extent that it can no longer be heldin the feed device 16. Thereafter the dressing apparatus 1 arrangedtherebehind is used for dressing the grinding tool 2. The empty locationwhich thereby occurs in the magazine 1 can be filled up by a furtherdressing apparatus 1.

In the embodiment shown in FIG. 4a the feed device 16 includes amagazine 17 which, in comparison with the magazine shown in FIG. 3, hason the one hand a loading device 27 for re-loading the dressingapparatuses 1 as well as an actuator 25 for the forward feed of thedressing apparatuses 1 in the direction of the grinding tool 2 to bedressed. In the illustrated situation dressing apparatuses 1 accordingto the second preferred embodiment are disposed in the magazine 17.Alternatively or supplementally dressing apparatuses 1 according to thefirst preferred embodiment can also be arranged in the magazine 17.

In addition there is provided a catch device 29 in which residues, whichhave not been used, of the dressing apparatuses 1 can be collected. Ifthis involves dressing apparatuses 1 according to the second preferredembodiment the residues substantially consist of the holding regions 9of the dressing apparatuses 1. If dressing apparatuses 1 according tothe first preferred embodiment are involved then the residuessubstantially consist of pieces of the dressing regions 3 and/or 4.

FIG. 4b shows an embodiment in which the feed device 16 is displaceablein the direction of the grinding tool 2 or in the reverse direction byway of a manual feed means 18, for example in the form of a spindledrive.

FIG. 4c shows an embodiment in which the dressing apparatuses 1 can beconveyed into an active dressing position from the magazine 17 fullyautomatically by means of an actuator 25 which is actuated by anautomatic delivery device. In addition there is provided a detectiondevice 24 with which the state of dressing apparatuses 1 in the magazine17 can be detected. Finally there is provided an open-loop and/orclosed-loop control device 20 which communicates at least with thedetection device 24 and the automatic delivery device 19.

FIG. 5 shows a diagrammatic enlarged view of a part of a dressingapparatus 1. The dressing region 4 includes a specification forrestoring the grinding profile of a grinding tool, wherein thatspecification involves a porosity in the range of 10 to 15 percent byvolume and a mixture of white corundum and pink corundum and/or redcorundum as abrasive grain of a grain size of about 55 mesh. Thedressing region 3 includes a specification for sharpening the grindingprofile of a grinding tool, wherein that specification involves a meanpore size of about 350 μm and white corundum as the abrasive grain of agrain size of about 180 mesh.

FIG. 6a diagrammatically shows the dressing step of profiling a grindingtool 2 with a dressing apparatus 1, in which case the grinding tool 2comes into contact with the dressing region 4. In that situation thedressing region 4 is used up until the grinding tool 2 comes intocontact with the dressing region 3 (see FIG. 6b ) and the sharpeningdressing step automatically takes place. It is appropriate for themethod step of restoring the grinding profile of a grinding tool to berepeated at a frequency N1 and for the sharpening method step to berepeated at a frequency N2, wherein N1<N2.

The change from restoring the grinding profile to sharpening is alsoshown once again diagrammatically in the upper part of FIG. 7. The lowerpart of FIG. 7 shows the option whereby the grinding tool 2 can be useda plurality of times for grinding at least one workpiece 15, preferablya glass pane, prior to the first method step 11 and/or between the firstand second method steps 11 and 12 and/or after the second method step 12and/or between an optionally provided repetition of the first or secondmethod steps 11 and 12.

1. A dressing apparatus for dressing a grinding tool provided with apredetermined grinding profile, wherein the dressing apparatus includesat least a first dressing region and a second dressing region connectedthereto, wherein the first dressing region has a first specification forsharpening the grinding profile of the grinding tool and the seconddressing region has a second specification differing from the firstspecification for restoring the grinding profile of the grinding tool,the first dressing region is of a larger volume than the second dressingregion, the dressing apparatus has a longitudinal axis, the two dressingregion are arranged in succession in the direction of the longitudinalaxis and the dressing apparatus is of a substantially cuboidalconfiguration.
 2. The dressing apparatus according to claim 1, whereinthe volume of the first dressing region is about 4 to 7 times,preferably about 6 times, greater than the volume of the second dressingregion.
 3. The dressing apparatus according to claim 1, wherein thedressing apparatus has: a length of 150 mm to 250 mm, particularlypreferably 180 mm to 200 mm, and/or a width of 25 mm to 75 mm,particularly preferably about 50 mm, and/or a thickness of 2.0 mm to10.0 mm, particularly preferably about 3.0 mm, 4.0 mm or 5.5 mm.
 4. Thedressing apparatus according to claim 1, wherein the firstspecification: has a mean pore size of 200 to 500 μm, preferably about350 μm, and/or has white corundum as the abrasive grain, and/or has anabrasive grain of a grain size of 120 to 220 mesh, preferably about 180mesh.
 5. The dressing apparatus according to claim 1, wherein the secondspecification: has a porosity in the range of 10 to 15 percent byvolume, and/or has a mixture of white corundum and pink corundum and/orred corundum as the abrasive grain, and/or has an abrasive grain with agrain size of 35 to 100 mesh, preferably about 55 mesh.
 6. The dressingapparatus according to claim 1, wherein the dressing apparatus has aholding region for holding the dressing apparatus when dressing thegrinding tool, preferably wherein: the holding region is of an abrasivegrain-less nature and/or is secured by adhesive or sintering, and/orsubstantially comprises a water-soluble material.
 7. A method ofdressing a grinding tool by the dressing apparatus according to claim 1,including a first method step in which the grinding profile of thegrinding tool is restored by means of the second dressing region of theat least one dressing apparatus, and a second method step in which thegrinding profile of the grinding tool is sharpened by means of the firstdressing region of the at least one dressing apparatus.
 8. The methodaccording to claim 7, wherein the first method step is repeated at afirst frequency before the second method step is carried out and thesecond method step is repeated at a second frequency after conclusion ofthe first method step which is repeated at the frequency N1, whereinN1<N2.
 9. The method according to claim 7, wherein, before the secondmethod step is carried out the first method step is carried out orrepeated until at least a predominant part of the second dressing regionis used up and after conclusion of the first method step the secondmethod step is carried out or repeated until at least a predominant partof the first dressing region is used up.
 10. The method according toclaim 7, wherein the grinding tool is used a plurality of times forgrinding at least one workpiece, preferably a glass pane, before thefirst method step and/or between the first and second method stepsand/or after the second method step and/or between an optionallyprovided repetition of the first or second method step.
 11. The methodaccording to claim 7, wherein the dressing apparatus has a holdingregion for holding the dressing apparatus when dressing the grindingtool and the at least one dressing apparatus is held at least at theholding region in a feed device at least during the first and secondmethod steps.
 12. The method according to claim 7, wherein the method iscarried out sequentially with a plurality of successive dressingapparatuses, wherein a further dressing apparatus, is fed preferablyfrom a magazine as soon as a preceding dressing apparatus is used up atleast for the predominant part.
 13. The method according to claim 7,wherein the method takes place in fully automated mode at least for thepredominant part.